1. Field of the Invention
The invention relates to a gear set and a nutation gear set.
2. Description of the Related Art
Some of gear sets include two bevel gears in mesh with each other (for example, see Japanese Patent Application Publication No. 11-315908 (JP-A-11-315908)). In JP-A-11-315908, the first and second gears are in mesh with each other, and the second gear is inclined with respect to the first gear. The first gear has a plurality of grooves, and rollers are arranged in the grooves so as to protrude from the grooves. The rollers form semi-cylindrical convex teeth. On the other hand, the second gear has a plurality of grooves, and has semi-cylindrical concave teeth. Then, as the first gear rotates, part of the convex teeth of the first gear are in mesh with part of the concave teeth of the second gear. Thus, the first gear rotates the second gear.
A situation that the rollers that constitute the convex teeth lift from the grooves of the first gear or slip off from the grooves (tooth jumping) leads to a torque loss or occurrence of noise, so it is undesirable. JP-A-11-315908 is not intended to actively press the rollers against the grooves of the first gear, so it is insufficient to prevent the rollers from lifting from the grooves of the first gear or slipping off from the grooves.